Finasteride is commonly prescribed as Propecia for male pattern hair loss and as Proscar for benign prostatic hyperplasia (BPH), an enlarged prostate. The drug works by influencing the body’s hormonal environment, which raises questions about its potential effects on male reproductive function. Given that many men taking this medication are of reproductive age, understanding its impact on fertility, particularly sperm count, is important. This article examines the scientific evidence to clarify the relationship between finasteride use and semen parameters.
Understanding the Hormonal Action of Finasteride
Finasteride works by targeting the enzyme 5-alpha reductase (5AR), primarily Type II, which is abundant in the prostate, hair follicles, and liver. This enzyme converts the male sex hormone testosterone into dihydrotestosterone (DHT), a more potent androgen. By blocking this conversion, finasteride significantly reduces the concentration of DHT in the blood and target tissues. This reduction in DHT is therapeutic for hair loss and BPH, but it also alters the hormonal balance involved in the production of sperm, known as spermatogenesis.
Clinical Findings on Sperm Count and Quality
Clinical studies show varying results depending on the finasteride dose and patient population. In healthy young men, the 1 mg daily dose used for hair loss generally shows no significant effect on sperm concentration, total sperm per ejaculate, or sperm morphology. Some studies noted a small reduction in semen volume with the 1 mg dose.
The higher 5 mg dose, used for BPH, has a more noticeable impact on semen parameters. One randomized study found that the 5 mg dose caused a decrease in total sperm count, sperm concentration, and sperm motility at 26 weeks. The reduction in sperm count for the 5 mg dose was reported to be around 34.3% at 26 weeks.
Effects on Subfertile Men
Concerns are greatest for men who already have underlying fertility issues, such as low sperm counts (oligospermia). Studies of men seeking fertility evaluations who were taking finasteride found that, even at the 1 mg dose, the medication might be associated with a drop in sperm counts. For these subfertile men, finasteride use was identified as a possible factor contributing to poor semen quality. Finasteride has also been associated with reduced sperm motility, but it does not typically affect sperm morphology.
Recovery of Sperm Parameters After Discontinuation
Any negative effects on sperm parameters from finasteride are generally reversible upon stopping the medication. Studies indicate that sperm concentration and quality tend to recover to baseline levels after treatment is discontinued. Recovery aligns with the cycle of spermatogenesis, which takes approximately 74 days, leading to substantial increases in sperm concentration within three to six months. For men with severe oligospermia, one study observed an average 11.6-fold increase in sperm count after discontinuation, with the majority returning to normal ranges. Men planning conception or who have existing fertility concerns should consult with a fertility specialist before or while taking the medication.